1. Field of the Invention
The present invention relates to polyallylamine conjugates and applications thereof for biological signal amplification, which enhance the biological signal intensity of trace molecules by utilizing the amino group of polyallylamine repeating unit to covalently bind with signal molecules and capture agents.
2. Description of Related Art
Spurred by the vigorous development of biomedical technology, broadened research fields and rapid expansion of applications, a great number of screening procedures have been developed. The most notable of them is the mapping of human genomes, followed by the successful applications of gene chips in the study of gene functionality. However, cell physiology is in fact affected by proteins. Unlike working on mRNA level, proteins in cells would interact with other proteins, small molecules or drugs, or perform other functions only after undergoing post-translation modification and sorting. That information on the mechanism of protein interactions is not obtainable independently; making the development of protein chips all the more important. Currently protein chips are applied in immunoanalysis, research of protein-to-protein interaction, research of gene expression mechanism, and cell-to-cell interaction. In light that the functional activity of protein is related to its stereo structure, making protein chip is a more complex than making gene chip. Aside from modeling after the DNA chip technology, there are quite a few key technologies to overcome in the making of protein chips, for examples: (1) How to immobilize biologically active protein on the chip? (2) How to identify the immobilized trace protein? (3) How to obtain definitive detection results from trace protein? As for the third technical problem, protein is different from DNA or RNA, which may be amplified by means of polymerase chain reaction (PCR). Thus it is rather important to grasp the technique for detecting low level of protein that binds on the chip.
U.S. Pat. No. 5,891,741 discloses the use of a dextran or polylysine conjugate to amplify the biological signals. But when dextran or polylysine is employed, self-quenching of fluorescence emission from the signal molecules, that is, the fluorescent molecules bound on the same polymer molecule, occurs due to short distances between the fluorescent molecules. The resulting offset of the original signal intensity weakens the signal expression instead. In addition, the short chain length of polylysine tends to create steric hindrance, while dextran requires modification, such as peroxidation to generate —COH or increasing —NH or other functional groups to aid its binding with the signal molecules, in which the degree of peroxidation poses another big variable. Thus the signal amplification procedure using dextran or polylysine is both complicated and hard to control.